The present invention relates to a torque adjusting apparatus and more particularly to a removable clutching mechanism for varying the torque required to turn a rotatable shaft.
In many instrument systems, conventional knobs are used to control various functions to the system. Such knobs are coupled through rotating shafts to control individual elements including switches, gear trains, potentiometers, indicators, and a variety of other elements. These elements are used in all types of instrument systems including avionics systems located in the cockpit of an aircraft. Normally, the torque required to turn the knobs is fixed by the particle construction of each of the individual elements and cannot be independently and variably adjusted. This means that the torque required to operate the shaft of any element is usually set by the manufacturer and varies greatly between individual elements and manufacturers of those elements.
In avionics systems particularly, the instruments located in the cockpit of an aircraft are usually confined to a limited area for easy access by the pilot and other cockpit personnel. The space limitations for such systems requires multi-function instruments which often include numerous knobs and switches in a very small area. Experience has shown that proper operation of the instruments is often dependent upon the tactile characteristics of the various knobs and switches. The right "feel" of those knobs and switches will thus affect the correct and efficient operation of the individual elements which they control. The torque on the shaft turned by such knobs is one of the tactile characteristics which contributes to the proper "feel" during operation. Naturally, the proper torque will significantly vary between operators and can therefore not be preset when various operators are using the same devices. The predetermined torque settings of conventional elements are therefore incapable of meeting individual operator preferences.
In the crowded cockpit environment, an additional problem encountered is that of inadvertent bumping or turning of adjacent knobs when the primary knob is being rotated. If the torque required to turn an adjacent knob is insufficient, a slight bump or brush may cause significant turning of the adjacent knob thereby destroying the setting of its element. In avionics systems particularly, the prevention of such inadvertent movement may be critical in preventing improper aircraft flight control as well as in preventing waste of pilot or operator time for resetting bumped or jarred knobs. With the preset element torques, greater care is required to prevent inadvertent rotation thereby taking up critical operator time, especially in busy flight environments.
Various techniques have been proposed to overcome the above problems. Some of those techniques have used spring and clutch arrangements which provide a force against the rotating shaft to increase the torque required to turn it. In most cases, such devices are designed to provide a one-time increase in the torque required to turn the shafts and thus are incapable of being adjusted. Over the course of time, wear on the shaft or clutch elements changes the torque required to turn the shaft so that the above problems are again encountered. The elements must then be repaired with the attendent expense increasing the life-cycle costs of the instruments.
In other instances, conventional devices are unacceptable because of the need for torque adjusting elements of small size. In avionics systems particularly, the constraints of the cockpit make it essential that miniaturization of elements be accomplished if at all possible. Prior devices have been complex and cumbersome and not suitable for cockpit use.
Accordingly, the present invention has been developed to overcome the shortcomings of the above known and similar techniques and to provide an improved clutch mechanism for variably controlling the torque required to turn a rotatable shaft.